Question: The scale on a map is 4cm : 8km. If the distance between two cities is 64km, how far apart in cm are the two cities on the map?
Explanation: The scale means that every 4cm on the map corresponds to an actual distance of 8km. An actual distance of 64km is the same as 8 $\cdot$ 8km. The distance between the two cities on the map is 8 $\cdot$ 4cm, or 32cm.